Histology Ch. 2 Flashcards
The Cytoplasm (155 cards)
1
Q
What are the basic structural and functional units of animal tissues?
A
Cells
Cells are the smallest living parts of the body.
2
Q
What type of cells are enclosed by cell membranes and are eukaryotic?
A
Animal cells
Each animal cell has a distinct, membrane-enclosed nucleus.
3
Q
What is the single cell formed by the merger of a spermatozoon with an oocyte called?
A
Zygote
4
Q
What are the first cellular divisions of the zygote called?
A
Blastomeres
5
Q
What type of stem cells arise from the inner cell mass of the early embryo?
A
Embryonic stem cells
6
Q
What process do most cells of the fetus undergo to become specialized?
A
Differentiation
7
Q
What do muscle cell precursors elongate into?
A
Long, fiber-like cells
8
Q
Which proteins are predominantly involved in muscle cell contractions?
A
Actin and myosin
9
Q
True or False: All animal cells contain actin filaments and myosins.
A
True
10
Q
What is the role of the plasma membrane?
A
Regulating the passage of materials into and out of the cell
11
Q
What are the major components of the plasma membrane?
A
Phospholipids, cholesterol, and proteins
12
Q
Fill in the blank: Membrane phospholipids are _______.
A
Amphipathic
13
Q
What structure do phospholipids form in the plasma membrane?
A
Bilayer
14
Q
What role does cholesterol play in the plasma membrane?
A
Modulates fluidity
15
Q
What do glycolipids contribute to on the cell surface?
A
Glycocalyx
16
Q
What type of proteins are incorporated directly within the lipid bilayer?
A
Integral proteins
17
Q
What distinguishes transmembrane proteins?
A
They span the membrane multiple times
18
Q
What type of proteins are bound to one of the membrane surfaces?
A
Peripheral proteins
19
Q
What is the fluid mosaic model?
A
A representation of membrane structure where proteins move within the fluid lipid bilayer
20
Q
What are lipid rafts?
A
Specialized membrane patches with higher concentrations of cholesterol and saturated fatty acids
21
Q
What is the main function of aquaporins?
A
Facilitating water transport across the plasma membrane
22
Q
What is the difference between passive transport and active transport?
A
Passive transport does not require energy, while active transport does
23
Q
What are pumps in the context of membrane transport?
A
Carrier proteins for active transport that require ATP
24
Q
What is phagocytosis?
A
The ingestion of particles such as bacteria or dead cell remnants
25
What type of cells are specialized for phagocytosis?
Macrophages and neutrophils
26
What is phagocytosis?
Ingestion of particles such as bacteria or dead cell remnants
## Footnote
Specialized cells like macrophages and neutrophils perform this process.
27
What is pinocytosis?
Involves smaller invaginations of the cell membrane that entrap extracellular fluid and its dissolved contents
## Footnote
The resulting vesicles are about 80 nm in diameter.
28
What is receptor-mediated endocytosis?
Involves receptors that bind specific ligands, leading to invagination and vesicle formation
## Footnote
This process is critical for transporting substances like low-density lipoproteins.
29
What are the three major types of endocytosis?
* Phagocytosis
* Pinocytosis
* Receptor-mediated endocytosis
## Footnote
Each type has distinct mechanisms and functions.
30
What is the phagosome?
An intracellular vacuole that encloses a bacterium after phagocytosis
## Footnote
It merges with a lysosome for degradation of its contents.
31
What is transcytosis?
The process where pinocytotic vesicles move to the opposite cell surface and release their contents outside the cell
## Footnote
It accomplishes bulk transfer of dissolved substances.
32
What role does clathrin play in endocytosis?
Forms a cage-like structure that helps invaginate the membrane to form coated vesicles
## Footnote
Clathrin is a major protein in the coating of these vesicles.
33
What are caveolae?
Invaginations in very thin cells involved in receptor-mediated endocytosis
## Footnote
They involve caveolins and cavins.
34
What triggers exocytosis?
A transient increase in cytosolic Ca2+
## Footnote
This process is highly regulated and involves specific membrane proteins.
35
What is constitutive secretion?
Release of products continuously as soon as synthesis is complete
## Footnote
An example includes collagen subunits for the extracellular matrix.
36
What is regulated secretion?
Release in response to specific signals coming to the cells
## Footnote
An example includes the release of digestive enzymes from pancreatic cells.
37
What are multivesicular bodies?
Subpopulations of vacuoles that accumulate small vesicles within their lumens
## Footnote
They may merge with lysosomes or fuse with the plasma membrane to release exosomes.
38
What are the four types of signaling processes?
* Endocrine signaling
* Paracrine signaling
* Synaptic signaling
* Autocrine signaling
* Juxtacrine signaling
## Footnote
Each type has a specific mechanism for signal transmission.
39
What are channel-linked receptors?
Receptors that open associated channels upon ligand binding to allow ion transfer across the membrane
## Footnote
They play a crucial role in signaling for neurotransmitters.
40
What are second messengers?
* Cyclic adenosine monophosphate (cAMP)
* 1,2-diacylglycerol (DAG)
* Inositol 1,4,5-triphosphate (IP3)
## Footnote
They amplify the initial signal in signal transduction pathways.
41
What is the function of ribosomes?
Assemble polypeptides from amino acids on tRNA according to mRNA sequences
## Footnote
They are essential for protein synthesis.
42
What are polyribosomes?
Complexes formed by multiple ribosomes binding the same strand of mRNA
## Footnote
They indicate sites of active protein synthesis.
43
What are polyribosomes?
Larger complexes formed when multiple ribosomes bind the same strand of mRNA.
44
Why do polyribosomes stain intensely in stained preparations?
They are intensely basophilic due to the polyanionic nature of phosphate groups in their RNA molecules.
45
What types of proteins do free polyribosomes synthesize?
* Cytosolic proteins
* Cytoskeletal proteins
* Proteins for import into the nucleus, mitochondria, and peroxisomes.
46
What types of proteins are synthesized on polysomes attached to the endoplasmic reticulum?
* Membrane proteins
* Lysosomal proteins
* Secreted proteins.
47
What happens to misfolded proteins during translation?
They are conjugated to ubiquitin and targeted for proteasomal degradation.
48
What is the structure of the endoplasmic reticulum (ER)?
A convoluted membranous network that extends from the nucleus throughout the cytoplasm, enclosing intercommunicating channels called cisternae.
49
What are the two types of endoplasmic reticulum?
* Rough Endoplasmic Reticulum (RER)
* Smooth Endoplasmic Reticulum (SER).
50
What characterizes the rough endoplasmic reticulum (RER)?
It is studded with polyribosomes and is the primary site for the synthesis of membrane-bound proteins.
51
What are the three main functions of the smooth endoplasmic reticulum (SER)?
* Lipid biosynthesis
* Detoxification of potentially harmful compounds
* Sequestration of Ca++ ions.
52
What is the role of the signal-recognition particle (SRP) during protein synthesis?
It binds to the signal sequence of the nascent polypeptide and directs the ribosome to the ER membrane.
53
What is ER-associated degradation (ERAD)?
The process where misfolded proteins are translocated back into the cytosol, conjugated to ubiquitin, and degraded by proteasomes.
54
What is the primary function of the Golgi apparatus?
To complete posttranslational modifications of proteins and package them for their proper destinations.
55
What are the two functional sides of the Golgi apparatus?
* Cis face (receiving side)
* Trans face (shipping side).
56
What are the three main activities associated with the rough endoplasmic reticulum?
* Production of membrane-associated proteins
* Initial glycosylation of glycoproteins
* Assembly of multichain proteins.
57
What is the significance of the N-terminal signal sequence in proteins destined for the RER?
It directs the nascent polypeptide to the ER for proper folding and processing.
58
What is one medical application related to the smooth endoplasmic reticulum?
Jaundice in newborns can occur due to underdeveloped SER in liver cells.
59
What are the distinct histological features of cells based on their protein synthesis activities?
* Cells with scant RER have free polyribosomes
* Cells storing proteins have RER and Golgi apparatus
* Epithelial cells specialized for secretion have distinct polarity.
60
What happens to proteins synthesized in the RER that cannot be properly folded?
They undergo ER-associated degradation (ERAD) and are targeted for proteasomal degradation.
61
What is the role of chaperones in the endoplasmic reticulum?
To assist in the proper folding of new proteins and prevent aggregation.
62
Fill in the blank: The Golgi apparatus is named after the histologist _____ who discovered it in 1898.
[Camillo Golgi]
63
True or False: The Golgi apparatus is a static structure with a fixed number of vesicles.
False
64
What type of vesicles move along cytoskeletal polymers?
Transport vesicles
## Footnote
These vesicles are moved by motor proteins.
65
What is the cis face of the Golgi apparatus?
The receiving region for transport vesicles
## Footnote
It is the side where vesicles merge with the Golgi.
66
What accumulates at the trans face of the Golgi apparatus?
Larger saccules or vacuoles
## Footnote
These generate vesicles that carry completed protein products.
67
What regulates vesicular traffic to and through the Golgi apparatus?
Protein coat complexes
## Footnote
These are involved in the formation of transport and secretory vesicles.
68
What is COP-II responsible for?
Forward movement of vesicles in the cis Golgi network
## Footnote
It sorts and concentrates proteins exiting the rough endoplasmic reticulum (RER).
69
What types of modifications occur in the Golgi apparatus?
Glycosylation, sulfation, phosphorylation, limited proteolysis
## Footnote
These modifications are performed by enzymes at different levels of the Golgi.
70
What are secretory granules?
Membrane-bound granules that store products until release
## Footnote
They are often involved in regulated secretion.
71
What is a zymogen granule?
Secretory granules containing digestive enzymes
## Footnote
These are found in gastrointestinal cells.
72
What are lysosomes primarily involved in?
Intracellular digestion and turnover of cellular components
## Footnote
They contain hydrolytic enzymes for breaking down macromolecules.
73
What types of enzymes do lysosomes commonly contain?
Acid hydrolases
## Footnote
Examples include proteases, nucleases, and phosphatases.
74
What is the pH of lysosomal enzymes for optimal activity?
~5.0
## Footnote
This is acidic compared to the cytosolic pH of ~7.2.
75
What is the function of mannose-6-phosphate (M6P) in lysosomal enzyme targeting?
It directs enzymes to lysosomes
## Footnote
This modification occurs in the cis Golgi.
76
What happens when endocytosed material fuses with lysosomes?
It mixes with lysosomal enzymes for digestion
## Footnote
This forms secondary or heterolysosomes.
77
What is autophagy?
Process of degrading excess organelles or nonfunctional macromolecules
## Footnote
It involves lysosomes and is enhanced by cell starvation.
78
What are proteasomes?
Cytoplasmic and nuclear protein complexes that degrade nonfunctional polypeptides
## Footnote
They are membrane-free and function differently from lysosomes.
79
What is ubiquitin?
A protein that tags other proteins for degradation by proteasomes
## Footnote
It is involved in the regulation of protein lifespan.
80
What are the two compartments created by the membranes of mitochondria?
The innermost matrix and intermembrane space
## Footnote
These compartments have different functions and compositions.
81
What is the primary function of mitochondria?
Production of adenosine triphosphate (ATP)
## Footnote
They specialize in aerobic respiration.
82
What is the significance of mitochondrial DNA mutations?
They can lead to diseases like myoclonic epilepsy with ragged-red fibers (MERRF)
## Footnote
These mutations affect respiratory chain proteins.
83
What is a residual body?
A vacuolar remnant of indigestible material in lysosomes
## Footnote
It can accumulate in long-lived cells as lipofuscin.
84
True or False: Lysosomes are well shown on H&E-stained cells.
False
## Footnote
They are better visualized after specific staining.
85
What are transmembrane proteins called that form channels for small molecules in mitochondria?
Porins
## Footnote
Porins allow metabolites like pyruvate to pass from the cytoplasm to the intermembrane space.
86
In what type of cells are mitochondria usually more abundant due to higher energy demands?
Cells undergoing active transport
## Footnote
Mitochondria appear as small eosinophilic structures in these cells.
87
What structures increase the surface area of the inner mitochondrial membrane?
Cristae
## Footnote
The inner membrane has sharp folds called cristae.
88
What is the primary function of ATP synthase in mitochondria?
To produce ATP
## Footnote
ATP synthase converts proton flow into mechanical energy, which is stored in ATP.
89
What do the enzymes in the mitochondrial matrix convert pyruvate into?
Acetyl CoA
## Footnote
This conversion occurs during the citric acid cycle.
90
What is the process called that produces most of the ATP in animal cells?
Oxidative phosphorylation
## Footnote
Enzymes in the inner membrane facilitate this process.
91
What role does cytochrome c play during cell stress?
Activates apoptosis
## Footnote
Cytochrome c dislodges and activates enzymes that degrade cellular components.
92
How do new mitochondria originate?
Growth and division of preexisting mitochondria
## Footnote
Each daughter cell typically receives half of the parent cell's mitochondria.
93
What type of DNA is found in the mitochondrial matrix?
Circular chromosome
## Footnote
This DNA is similar to bacterial components.
94
What are peroxisomes primarily known for?
Producing and degrading hydrogen peroxide
## Footnote
They contain oxidases and peroxidases to manage hydrogen peroxide.
95
What is the function of catalase in peroxisomes?
Breaks down hydrogen peroxide
## Footnote
Catalase converts H2O2 into water and oxygen.
96
What type of fatty acids do peroxisomes preferentially oxidize?
Long-chain fatty acids (18 carbons and longer)
## Footnote
This process utilizes specific peroxisomal enzymes.
97
What are the three main components of the cytoplasmic cytoskeleton?
* Microtubules
* Microfilaments (actin filaments)
* Intermediate filaments
## Footnote
These components play key roles in cell shape and movement.
98
What is the diameter of a microtubule?
25 nm
## Footnote
Microtubules are hollow structures contributing to cell rigidity.
99
What is a heterodimer in the context of microtubules?
A combination of α and β tubulin
## Footnote
Each has a molecular mass of about 50 kDa.
100
What is dynamic instability in microtubules?
Continuous cycles of polymerization and depolymerization
## Footnote
This phenomenon allows microtubules to explore the cytoplasm.
101
What structure serves as the dominant microtubule-organizing center in most cells?
Centrosome
## Footnote
The centrosome consists of paired centrioles.
102
What occurs to the centrosome during DNA replication?
It duplicates to form two centrosomes
## Footnote
Each centrosome contains a pair of centrioles.
103
What is the function of the centrosome during mitosis?
The centrosome becomes an organizing center for the microtubules of the mitotic spindle.
## Footnote
The centrosome duplicates itself to form two centrosomes that move to opposite poles of the cell.
104
How are centrioles structured within a centrosome?
Each centriole consists of nine microtubular triplets and exists at right angles to each other.
## Footnote
This structure is embedded in a dense matrix of free tubulin subunits and other proteins.
105
What happens to the centrosomes during a cell's interphase?
The centrosome duplicates and each half has a duplicated centriole pair.
## Footnote
This process is poorly understood.
106
What role do microtubules play in intracellular transport?
Microtubules facilitate the transport of membranous vesicles, macromolecular complexes, and organelles.
## Footnote
Examples include axoplasmic transport in neurons and vesicle movements among different cell compartments.
107
What are motor proteins and what do they do?
Motor proteins facilitate movement along microtubules using ATP.
## Footnote
Kinesins carry materials away from the MTOC, while dyneins transport materials toward the nucleus.
108
Name three drugs used in cancer chemotherapy that affect microtubules.
* Vinblastine
* Vincristine
* Paclitaxel
## Footnote
These compounds block the activity of the mitotic spindle in rapidly growing neoplastic cells.
109
What are microfilaments composed of?
Microfilaments are composed of actin subunits.
## Footnote
They allow motility and contractile activity in cells.
110
Describe the structure of actin filaments.
Actin filaments are thin, polarized polymers made of globular G-actin monomers.
## Footnote
G-actin assembles into a double-stranded helix of filamentous F-actin.
111
What is treadmilling in actin filaments?
Treadmilling is the process where monomers polymerize rapidly at the (+) end and dissociate at the (−) end.
## Footnote
This leads to a net movement or flow along the polymer.
112
What is the primary role of Arp2/3 in actin filament dynamics?
Arp2/3 binds to preexisting actin filaments and induces the formation of new F-actin branches.
## Footnote
This process contributes to the formation of a microfilament network.
113
What are some functions of myosin motors in relation to actin filaments?
Myosin motors transport cargo, facilitate cytoplasmic streaming, and produce cell surface changes during endocytosis.
## Footnote
Conventional myosin moves toward the barbed (+) ends, while unconventional myosin VI moves in the opposite direction.
114
What are intermediate filaments and their average diameter?
Intermediate filaments are cytoskeletal components averaging 10 nm in diameter.
## Footnote
They provide mechanical stability to cell structure.
115
Name a key protein found in intermediate filaments.
Keratins (cytokeratins) are a key class of proteins in intermediate filaments.
## Footnote
They form heterodimer subunits in epithelial cells and are important for keratinization.
116
What is the role of vimentin in intermediate filaments?
Vimentin is the most common class III intermediate filament protein found in cells derived from embryonic mesenchyme.
## Footnote
It is important in muscle cells and astrocytes.
117
What are cytoplasmic inclusions?
Cytoplasmic inclusions are structures containing accumulated metabolites or substances with little or no metabolic activity.
## Footnote
They are typically transitory and not enclosed by membranes.
118
List three types of cytoplasmic inclusions.
* Lipid droplets
* Glycogen granules
* Pigmented deposits (e.g., melanin, lipofuscin, hemosiderin)
## Footnote
These inclusions serve various functions, such as energy storage or protection from UV radiation.
119
What is hemosiderosis?
Hemosiderosis is a condition characterized by the accumulation of hemosiderin in cells throughout the body.
## Footnote
It can result from increased dietary iron uptake or excessive lysis of red blood cells.
120
What is the plasma membrane?
The plasma membrane is the lipid bilayer with embedded proteins that surrounds a cell.
## Footnote
It is only visible with transmission electron microscopy (TEM).
121
What stabilizes the lipid bilayer of the plasma membrane?
Cholesterol stabilizes the lipid bilayer formed from amphipathic phospholipids.
## Footnote
This bilayer contains integral and peripheral proteins.
122
True or False: Integral membrane proteins can include receptors for external ligands.
True
## Footnote
They also include channels for passive transport.
123
What is the plasma membrane also known as?
Cell membrane or plasmalemma
124
What stabilizes the lipid bilayer of the plasma membrane?
Cholesterol
125
What types of proteins are embedded in the lipid bilayer?
* Integral proteins
* Peripheral proteins
126
What are lipid rafts?
Areas with higher concentrations of cholesterol and saturated fatty acids
127
Name three functions of integral membrane proteins.
* Receptors for external ligands
* Channels for movement of molecules
* Pumps for active membrane transport
128
What is endocytosis?
Cellular uptake of macromolecules or fluid by plasma membrane engulfment
129
What are the major types of endocytosis?
* Phagocytosis
* Pinocytosis
* Receptor-mediated endocytosis
130
What is exocytosis?
Cellular secretion where vesicles fuse with the plasma membrane
131
What role do membrane receptor proteins play in cell signaling?
They initiate intracellular signaling pathways
132
What are ribosomes made of?
rRNA and many proteins
133
What is a polyribosome?
Multiple ribosomes on the same mRNA
134
What does the rough endoplasmic reticulum (RER) primarily do?
Makes most membrane proteins and proteins for exocytosis
135
What is the function of signal peptides in the RER?
They bind receptors in the ER membrane to localize proteins
136
What does the smooth endoplasmic reticulum (SER) lack?
Ribosomes
137
What processes does the SER include?
* Lipid metabolism
* Glycogen metabolism
* Detoxification reactions
* Ca2+ sequestration
138
What is the Golgi apparatus?
An organelle that processes and packages proteins made in the RER
139
What modifications do proteins undergo in the Golgi apparatus?
* Sulfation
* Glycosylation
140
What are primary lysosomes?
Lysosomes containing inactive acid hydrolases
141
What are secondary lysosomes?
Lysosomes that have fused with endocytosed vesicles
142
What is autophagy?
The process by which lysosomes digest unneeded organelles
143
What are proteasomes responsible for?
Degrading improperly folded proteins tagged with ubiquitin
144
What are mitochondria known for?
Major sites of ATP synthesis
145
How do mitochondria replicate?
By fission of preexisting mitochondria
146
What is the structure of mitochondria?
* Outer membrane
* Inner membrane with folds (cristae)
* Gel-like matrix
147
What happens to mitochondria in stressed cells?
They may release cytochrome c, triggering apoptosis
148
What do peroxisomes contain enzymes for?
Oxidation and detoxification reactions
149
What are the three types of polymers in the cytoskeleton?
* Microtubules
* Actin filaments (microfilaments)
* Intermediate filaments
150
What is the diameter of microtubules?
25 nm
151
What are microfilaments composed of?
Actin subunits
152
What do myosins do?
Bind and move along actin filaments
153
What is the role of intermediate filaments?
Conferring strong mechanical stability to cells
154
What are inclusions?
Storage sites that are not metabolically active
155
Name two types of inclusions.
* Lipid droplets
* Glycogen granules
